中文摘要：

膝状挠曲破碎带是某水电站坝基的主要工程地质问题。破碎带岩性为完整性较差的碎裂、碎屑软弱砂岩，并呈现孔隙式胶结接触，其工程力学特性对坝基变形和稳定存在巨大影响。基于破碎带砂岩组织结构疏松、含水率较高、物理力学性能较差等特点，首先开展了基本物理特性试验分析，认为岩石微细观结构复杂、渗透特性较好，属小孔隙率砂岩。其次，开展了室内常规和现场力学特性试验研究；最后，在宏观力学参数确定的基础上，探讨了破碎带对工程作用的响应及影响。结果表明，破碎带岩石内部结构破坏严重，矿物成分主要为石英、长石、绢云母等，化学成分以SiOz为主，但化学侵蚀并不显著。常规剪切曲线呈现出明显的4阶段特征，三轴压缩试验破坏机制为塑性剪切破坏，表现出强度低、延性扩容明显、出现屈服平台等特征，且碎裂岩强度略高于碎屑岩；现场试验表明岩体变形均匀，变形模量较低，处于60~630MPa；地基承载力处于0．8～2_3MPa。研究成果对该水电站坝基工程有重要的参考价值。

英文摘要：

The knee-shaped deflection fractured zone located in the dam-foundation of a hydropower station is a main engineering geological problem of the project. The lithology is soft sandstone with poor integrity and pore cementation contact, which composed by cataclastic rock and clastic rock. The engineering mechanical properties of sandstone may have a significant impact on the deformation and stability of the dam. Based on the characteristics of loose organizational structure, high moisture content and poor physical mechanical properties, the basic physical properties tests are carried out to fractured zone sandstone first. It＇s considered the sandstone which is extremely complex microstructure and good permeability as small porosity sandstone. Secondly, the conventional and field tests are carded out to study mechanical properties. Finally, the influences of the fractured zone are discussed based on a certain macromechanical parameter. The results show that, the internal structure of sandstone is damage seriously; and main mineral compositions are quartz, feldspar, sericite and so on; the main chemical constituent is SiO2; but the chemical erosion is not significant. The shear curve shows the characteristics of four distinct stages. The failure mechanism oftriaxial compression test is plastic shearing; and the curve shows a low strength, significantly ductility dilatancy; and yield platform is formed. Also the cataclastic rock strength is slightly higher than clastic rock. The field tests show that the deformation of rock mass is uniform, but the deformation modulus is low of which the range is 60-630 MPa. And the foundation bearing capacity ranges from 0.8-2.3 MPa. The research results provide greatly referential value for dam foundation ofhydropower station.